Facile preparation of a water-based antireflective SiO 2 film with high transmittance for perovskite solar cells.

The synthesis of anti-reflective (AR) films has been increasingly focused on environmental friendliness and cost efficiency in order to realize green and sustainable development. Herein, a novel strategy for preparing a nanoporous SiO 2 AR film with high transmittance by a sol-gel process is proposed based on a sodium silicate aqueous solution. Sodium ions in the as-prepared SiO 2 AR film can be effectively removed by a facile washing process, and thus its refractive index can be regulated. Moreover, the pH value of the sol has a huge effect on the structure and properties of the SiO 2 AR film. As a result, the AR film exhibited a high transmittance increase of 4.10% at 550 nm and an average transmittance increase by 3.51% in the wavelength range of 380-1100 nm compared with blank glass. In addition, the obtained water-based SiO 2 AR film exhibited hydrophilicity and the water contact angle (WCA) can be regulated from 61° to 8.4°. When the AR film was applied to the upper surface of perovskite solar cells, the photoelectric conversion efficiency (PCE) revealed an improvement of 1.44% compared with the PCE of perovskite solar cells without the AR film. Therefore, this work can provide a facile and effective method to prepare water-based antireflective films with high transmittance for solar cells.